6th Annual Symposium
Physics of Cancer
September 7-9, 2015
|PoC - Physics of Cancer - Annual Symposium|
Signals and mechanics guiding cellular organization in epithelia
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Many epithelial tissues are organized into subpopulations of cells with distinct functions or fates. Maintaining straight boundaries between these different cell populations within tissues requires mechanisms to counteract cell rearrangements and cell mixing caused by cell division and tissue reshaping. Local increases in mechanical tension are important in segregating cell populations at boundaries within tissues, yet the signals that control increases in mechanical tension and the mechanisms by which mechanical tension influences cellular dynamics to segregate cell populations remain unknown. Here we demonstrate that the Hedgehog signaling pathway is necessary and sufficient to increase mechanical tension along the boundary between anterior and posterior cell populations in Drosophila wing imaginal discs. Moreover, by quantitatively analyzing cellular dynamics in the vicinity of tissue boundaries in pupal Drosophila histoblasts, we show that cell mixing within the same cell population involves multiple cell intercalations. Cells also intercalate along boundaries between different cell populations, junctional rearrangements during intercalation, however, are biased to disfavor cell mixing. Simulations of tissue growth with two cell populations suggest that local increases in mechanical tension can account for the observed bias in junctional rearrangements during intercalation. We propose that Hedgehog signaling induces local increases in mechanical tension and that mechanical tension guides cell segregation at tissue boundaries by biasing cell intercalations.